// Author: combacsa@kaist.ac.kr
// http://www.jungol.co.kr/prog/Hanal/hanalView.php?qs_code=1047

//#define COMPILE
#ifdef COMPILE

#include <fstream>

using namespace std;

int n;
int answer;

void input() {
    ifstream in("input.txt");
    in >> n;
    in.close();
}

void output() {
    ofstream out("output.txt");
    int a = 1;
    int b = 1;
    int c = 1;
    for (int i = 2; i < n; i++) {
        c = a + b;
        a = b;
        b = c;
    }
    out << c;
    out.close();
}

int main() {
    input();
    
    
    output();
    return 0;
}


#endif
